[X] My Assistant

[SFJCody]

Seems to be a lot of dispute on this subject... I think it's ice from the interior, but what does everyone else think?

Edit:

This world seems very complex so the question could perhaps be phrased as 'which of these options is most responsible for the Iapetan dichotomy?'

[tasp]

Here is another 'negative' print of Iapetus.

I am still thinking we are seeing a material not unlike silver nitrate applied to the Iapetan surface and 'developed' by exposure to sunlight.

The 'silver nitrate' analog is 'applied' as a gaseous efflux to Iapetus as it moves around the far side of Saturn, and dissipates to the void in ~40 days, with some 'ponding' in very low spots persisting longer.

The efflux may not persist as a gas in the Iapetan environment, it may absorb on to the surface materials, but it still manages to dissipate in less than 1 Iapetan day.

The material is sensitive to local heating effects, and local here can apparently be a matter of meters.

Note in the negative print the shadow like aspect of the dark areas.

The difficulty we are having in interpreting these images (regarding the black on white or white on black discussion) is perhaps due to the 'negative' visual characteristic of the actual appearance of the Cassini Regio 'crud'. Negative prints help visualize the effects of insolation on this 'silver nitrate' analog.

Attached thumbnail(s)